A study describing the amount, location, quality, and economic position
of low-sulfur strippable coal in the San Juan Basin, northwest New Mexico
and southwest Colorado. Study conducted by the New Mexico Bureau of Mines
and Mineral Resources for the Air Pollution Control Office of the Environmental
Protection Agency.

The report is a compendium
of short, more or less self-contained papers dealing with the various coal
fields and areas, and with other pertinent subjects. For the purposes of
study, coal reserves were estimated in two broad categories-those consisting
of beds three feet thick or thicker beneath 10150 ft of overburden,
and those in beds five or more feet thick beneath 150250 ft of overburden.
Data were gathered from all available sources and include: published geologic
work, original geologic observation, private consultants' reports, logs
of test holes drilled by holders of leases and exploration permits, logs
of holes drilled by the New Mexico Bureau of Mines and Mineral Resources, reserve
calculations furnished by operators, and information from oil and gas tests.
The best use was made of whatever data could be found for a particular area;
therefore reserve estimates range in reliability from proven tonnages to
speculation based on geologic inferences. An effort was made to give an
evaluation of the reliability of each estimate. Coal quality was determined
from published and unpublished analyses by the U.S. Bureau of Mines, analyses
furnished by operators, and U.S. Bureau of Mines analyses of samples collected
during the study.

The San Juan Basin is a major physiographic subdivision
of the Colorado Plateau in northwestern New Mexico and southwestern Colorado.
The basin is about 200 mi long (north to south) and 130 mi wide, and includes
about 26,000 mi2. The strippable coal areas lie along the basin's margins-mainly
the western and southern-in roughly concentric belts of outcrop of coal-bearing
strata of generally Cretaceous age, with rolling, sparsely grassed plains
interrupted by low cuestas and mesas, and broad sandy washes. Coal is found
in three major zones of the Cretaceous sequence. In ascending order, they
are: the Dakota Sandstone, the Mesaverde Group, and the Fruitland Formation;
the three are separated by barren strata of greatly varying thickness.